fix predictor initialization for adpcm-ima encoder not to lose first sample

in block in adpcm-ima decoder
Patch by Timofei V. Bondarenko: tim £ ipi, ac, ru
Original thread: [FFmpeg-devel] [PATCH] adpcm-ima-wav header and codec
Date: 10/15/2007 05:55 PM

Originally committed as revision 10933 to svn://svn.ffmpeg.org/ffmpeg/trunk